1. Field of the Invention
The present invention relates to an automatic transmission for a vehicle such as automobile, and more particularly to an automatic transmission for a vehicle having a transversely mounted engine.
2. Description of the Prior Art
The modern automatic transmission for a vehicle is generally of a hydro-mechanical type which generally comprises a torque converter and a speed change gear device connected in series in said order to the crankshaft of an engine, with an oil hydraulic pump to generate oil hydraulic pressure for operating the transmission being generally mounted at the rear end of the torque converter as therefore located between the torque converter and the speed change gear device. Such a hydro-mechanical automatic transmission for a vehicle generally includes a plurality of hydraulically operated clutches and brakes which are selectively engaged or disengaged in order to switch over the route of power transmission in the speed change gear device so as selectively to provide one of a plurality of speed stages or a reverse stage. One of those clutches is generally the so-called forward clutch which is engaged to provide forward speed stages such as 1st, 2nd and 3rd speed stages and is kept in engagement throughout forward running of the vehicle while other clutches and brakes are switched over between engagement and disengagement according to the speed stages to be achieved.
From the view point of further improving the speed stage shifting performance of the transmission to be more smooth with no abrupt acceleration or deceleration, it is contemplated to position said forward clutch as close to the oil hydraulic pump and as remote from the other clutches and brakes as possible so that the oil hydraulic pressure supplied to the forward clutch is less affected to fluctuate by engagement or disengagement of, i.e. supply of hydraulic oil to or discharge thereof from, the other clutches and brakes.
On the hand, in a vehicle having a transversely mounted engine in which an axial combination of the engine and the automatic transmission is arranged transversely in the vehicle, it is required that a power output member of the transmission is located generally at a transversely central portion of the vehicle so that the power output member can directly drive a front differential or the like which is generally mounted at a transversely central portion of the vehicle. A structure of automatic transmission in which the power output member thereof is positioned at an axially central portion of the combination of the torque converter and the speed change gear device is described in, for example, Japanese Patent Laying-open Publications 55-33948 (1980) and 57-87716 (1982). In these prior art structures the power output gear wheel member is positioned between the torque converter and the speed change gear device to be coaxial thereto, and between the oil hydraulic pump mounted at the rear end of the torque converter and the speed change gear device. However, all clutches and brakes are positioned on the same axial side of the power output member as the gear mechanism of the speed change gear device as intimately assembled therewith according to the conventional common concept in this art that these components are assembled to be as axially compact as possible to reduce the longitudinal size of the transmission, particularly in the transverse type transmission.
In Japanese Patent Laying-open Publication 58-163849 (1983) a structure of automatic transmission is disclosed in which a clutch is positioned between the torque converter and a power output member of the speed change gear device of an axial combination thereof. In this transmission the clutch C2 positioned between the torque converter and the power output member G2 is a clutch which is engaged when and only when the transmission provides a certain speed stage, and is not kept in engagement while other clutches or brakes are switched over between engagement and disengagement.